Positive air pressure (PAP) assisted ventilation systems have been adopted for the treatment of various disorders. PAP systems are commonly used to treatment sleep apnea. Variations of PAP systems have been used to administer drugs and the like.
In operation the patient's respiration is assisted by an external pump which supplies air to the patient under a slight positive pressure. In the conventional system, air is delivered in response to preset conditions selected for each individual patient. In normal operation the patient's inspiratory phase is assisted by a pump which delivers an adequate supply of air at a slight positive pressure to a mask or cannula that is placed on the face of the patient. Full face mask systems which cover both the mouth and the nose are used. Systems which cover the mouth or nose alone are also common.
In use, when the patient exhales, the higher pressure in the mask or cannula system is used to open an exhaust valve. Thus the patient respiration is assisted on the inhalation phase by positive pressure while the expiration phase takes place at approximately atmospheric pressure.
In instances where the patient compliance is affected by the comfort of the mask it is now widely accepted that “nose only” cannula devices are preferred. Examples of current devices can be seen in U.S. Pat. No. 5,477,852 to Landis; U.S. Pat. No. 5,533,506 to Wood; U.S. Pat. No. 5,269,296 to Landis; U.S. Pat. No. 5,687,715 to Landis; U.S. Pat. No. 5,724,965 to Handke.